48 PRODUCT PROFILE
Composite damper bodies
…Roman Bielak, technology development manager at BWI Group, discusses the trials and triumphs
of developing a composite damper body
ABOVE: Better dynamic suspension performance and improved vehicle
fuel efficiency are possible with BWI Group’s innovative composite
damper body
››The use of materials other
than steel and aluminium in
the design and manufacture of
automotive suspension parts has become
common practice for both suppliers and
auto manufacturers, bringing weight
benefi ts in terms of lighter materials
and slimmed-down components. With
components made from alternative
materials such as composites already
being used in chassis applications, the
question is not whether they can be
used, but what more can be done.
BWI Group specialises in fi nding
alternative materials to replace steel
and aluminium in shock absorbers, and
a number of its lightweight solutions
have already been successfully
implemented by customers. Roman
Bielak, technology development manager
at BWI Group, discusses the way forward
for lighter suspension components.
WHAT ARE THE PROS AND CONS
OF USING COMPOSITES
IN DYNAMICS COMPONENTS?
Composite materials have been tempting
suspension designers for some time,
as they have great potential to deliver
weight savings. Composite suspension
components can be easily manufactured
in high volume and in many different
forms, but there are offsetting factors:
performance over temperature and
performance over time, which must be
taken into account at the design stage.
Bearing in mind the potential that
composite materials bring, along with
their constraints, several years ago
BWI Group pioneered the application
of composite strut-spring-seats by
introducing a part with no steel
reinforcement into the market. This very
demanding application, with the spring
seat holding the weight of the vehicle
corner, is responsible for transferring
substantial static and dynamic loads,
and is linked with safety. It took several
years to develop these parts, analysing
parts with FEM, advancing moulding
technology and testing physical parts,
while accounting for the special
properties of composite materials. The
result was that the composite spring
seat offered a 50% reduction in mass,
compared to the equivalent steel
component.
VehicleDynamicsInternational.com •May/June 2020
WHAT OTHER APPLICATIONS
ARE THERE FOR COMPOSITES?
Motivated and inspired by the benefi ts
of composites, damper design engineers
have been evaluating other potential
applications, leading to the desire to
create a damper body fully comprised
of composite materials. The target
became a shock absorber body, with
possible extension to coil-overs.
However, for the time being, the
suspension strut has been ruled out due
to concerns over stiffness and knuckleclamping
challenges related to the
rheological properties of the favoured
composite material.
Another interesting challenge is
that composite materials are heat
isolators, which goes against one of
the primary functions of dampers:
transferring damping forces into heat,
and dissipating that heat into the
surrounding environment. A solution
has been found by increasing the surface
area of the composite damper body
through the addition of moulded ribs,
offsetting the slower heat conductivity
of the composite material by having
more surface area.
A further challenge is that integrating
a composite damper body with a steel
inner tube into a twin-tube shock
absorber design makes damper closure
design more diffi cult. Given the different
heat-expansion properties of the
materials used, additional features
must be implemented to secure the
internal preload on the inner tube
over the damper’s entire operational
temperature range.
HAVE THESE CHALLENGES
BEEN OVERCOME?
Bench testing has been completed,
and the damper is now ready for serial
production. BWI Group’s composite
damper body is an effective tool
with which automotive designers
can reduce vehicle weight, yielding
reduced emissions, improvements to
electric vehicle range, and improved
vehicle agility and suspension system
responsiveness.
READER ENQUIRY SERVICE
To learn more from BWI Group, visit
www.magupdate.co.uk/pvdi
“Composite suspension
components can be easily
manufactured in high volume and
in many diff erent forms, but there
are off setting factors”
/VehicleDynamicsInternational.com
/pvdi